It would take 38 hours for the one plane to do a return trip, I can't see them utilizing the plane more on a Short/Medium haul route to SIN, MEL or SYD but with the scheduling & routes V Australia do now it would not surprise me.
I guess the scenario you outline doesn't preclude the option of flying some of their other 777's across to PER and back. Not sure of the traffic ex-PER but you would think to get the big $$ in the J cabin they would need to supplement ex-PER traffic with ex-SYD/MEL traffic, and that means offering a J service across the continent to connect(I know in Europe they get away with J = Y seats with a little extra legroom and and empty seat in the middle, but that ain't going to cut it across the bight against SQ/QF/EK etc who give you a good seat all the way). Maybe we will see some DJ J cabins? Who knows.